354 M. Reichert on the Morphology and Motory Phenomena 
most frequently in the pseudopodia ; but their movement is ob- 
servable in all the processes, even in the unthickened and ele- 
vated contractile membrane, both within and outside the shell. 
d. On return to the so-called state of rest, each process retracts 
to exactly the same place in the contractile sac or the lamella 
as that from which the elevation occurred. In the branched 
forms the retraction commences at the terminal branches, and 
at the same time the movement of the granules ceases; that of 
the trunks follows. Hence it may be regarded as a law, that 
the particles of the contractile cortical layer protruded by the 
contraction, after return to the state of rest, he in exactly the 
same order and relative position as they did when the contrac- 
tion began. 
e. All motory phenomena in which large masses of the contrac- 
tile substance are concerned, exhibit a certain sluggishness at 
their commencement as well as at their recedence. A stout 
cylindrical process always requires a considerable time for its 
formation, during which new contractile matter is being added— 
as much as half an hour or even more ; the development of the 
more slender pseudopodia, and especially of the granules, takes 
place rapidly. 
f. The contractile action in the granular movement is more- 
over remarkable from the circumstance that in most cases, im- 
mediately after the state of rest has taken place, it causes a 
similar action in the adjoining contractile substance, producing 
a movement of waves, resulting from contraction, running in 
various directions. The law of these waves has not hitherto 
been determinable; according to appearances, the commence- 
ment, the cessation, and, in the case of the plates and mem- 
branes of the contractile substance, also the direction of the 
motion of the granules ensue with perfect irregularity. More- 
over, although the appearance of a so-called granule of the 
granule-movement gives rise to a similar contractile motion in 
the adjacent parts, yet instances have often occurred to me in 
which granules have appeared and remained, without setting a 
contraction-wave in motion. It may be regarded as a peculi- 
arity of the motory phenomenon of the contractile cortical layer, 
that every movement of contraction may remain at a certain 
state of intensity for several hours. 
Comparison of the Contractile Substance of the Bodies of the 
Polythalamia with Muscular Fibre. 
The comparison of the contractile cortical layer with muscu- 
lar fibre will refer exclusively to the morphological phenomena, 
and what may be deduced from them to illustrate the relative 
law of the contractile action. What takes place within the 
